/*
 * $Header:
 * /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons
 * //httpclient
 * /src/java/org/apache/commons/httpclient/ContentLengthInputStream.java,v 1.12
 * 2004/10/04 22:05:44 olegk Exp $ $Revision: 480424 $ $Date: 2006-11-29
 * 06:56:49 +0100 (Wed, 29 Nov 2006) $
 *
 * ====================================================================
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with this
 * work for additional information regarding copyright ownership. The ASF
 * licenses this file to You under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many individuals on
 * behalf of the Apache Software Foundation. For more information on the Apache
 * Software Foundation, please see <http://www.apache.org/>.
 */

package com.microsoft.tfs.core.httpclient;

import java.io.IOException;
import java.io.InputStream;

/**
 * Cuts the wrapped InputStream off after a specified number of bytes.
 *
 * <p>
 * Implementation note: Choices abound. One approach would pass through the
 * {@link InputStream#mark} and {@link InputStream#reset} calls to the
 * underlying stream. That's tricky, though, because you then have to start
 * duplicating the work of keeping track of how much a reset rewinds. Further,
 * you have to watch out for the "readLimit", and since the semantics for the
 * readLimit leave room for differing implementations, you might get into a lot
 * of trouble.
 * </p>
 *
 * <p>
 * Alternatively, you could make this class extend
 * {@link java.io.BufferedInputStream} and then use the protected members of
 * that class to avoid duplicated effort. That solution has the side effect of
 * adding yet another possible layer of buffering.
 * </p>
 *
 * <p>
 * Then, there is the simple choice, which this takes - simply don't support
 * {@link InputStream#mark} and {@link InputStream#reset}. That choice has the
 * added benefit of keeping this class very simple.
 * </p>
 *
 * @author Ortwin Glueck
 * @author Eric Johnson
 * @author <a href="mailto:mbowler@GargoyleSoftware.com">Mike Bowler</a>
 * @since 2.0
 */
public class ContentLengthInputStream extends InputStream {

    /**
     * The maximum number of bytes that can be read from the stream. Subsequent
     * read operations will return -1.
     */
    private final long contentLength;

    /** The current position */
    private long pos = 0;

    /** True if the stream is closed. */
    private boolean closed = false;

    /**
     * Wrapped input stream that all calls are delegated to.
     */
    private InputStream wrappedStream = null;

    /**
     * @deprecated use {@link #ContentLengthInputStream(InputStream, long)}
     *
     *             Creates a new length limited stream
     *
     * @param in
     *        The stream to wrap
     * @param contentLength
     *        The maximum number of bytes that can be read from the stream.
     *        Subsequent read operations will return -1.
     */
    @Deprecated
    public ContentLengthInputStream(final InputStream in, final int contentLength) {
        this(in, (long) contentLength);
    }

    /**
     * Creates a new length limited stream
     *
     * @param in
     *        The stream to wrap
     * @param contentLength
     *        The maximum number of bytes that can be read from the stream.
     *        Subsequent read operations will return -1.
     *
     * @since 3.0
     */
    public ContentLengthInputStream(final InputStream in, final long contentLength) {
        super();
        wrappedStream = in;
        this.contentLength = contentLength;
    }

    /**
     * <p>
     * Reads until the end of the known length of content.
     * </p>
     *
     * <p>
     * Does not close the underlying socket input, but instead leaves it primed
     * to parse the next response.
     * </p>
     *
     * @throws IOException
     *         If an IO problem occurs.
     */
    @Override
    public void close() throws IOException {
        if (!closed) {
            try {
                ChunkedInputStream.exhaustInputStream(this);
            } finally {
                // close after above so that we don't throw an exception trying
                // to read after closed!
                closed = true;
            }
        }
    }

    /**
     * Read the next byte from the stream
     *
     * @return The next byte or -1 if the end of stream has been reached.
     * @throws IOException
     *         If an IO problem occurs
     * @see java.io.InputStream#read()
     */
    @Override
    public int read() throws IOException {
        if (closed) {
            throw new IOException("Attempted read from closed stream.");
        }

        if (pos >= contentLength) {
            return -1;
        }
        pos++;
        return wrappedStream.read();
    }

    /**
     * Does standard {@link InputStream#read(byte[], int, int)} behavior, but
     * also notifies the watcher when the contents have been consumed.
     *
     * @param b
     *        The byte array to fill.
     * @param off
     *        Start filling at this position.
     * @param len
     *        The number of bytes to attempt to read.
     * @return The number of bytes read, or -1 if the end of content has been
     *         reached.
     *
     * @throws java.io.IOException
     *         Should an error occur on the wrapped stream.
     */
    @Override
    public int read(final byte[] b, final int off, int len) throws java.io.IOException {
        if (closed) {
            throw new IOException("Attempted read from closed stream.");
        }

        if (pos >= contentLength) {
            return -1;
        }

        if (pos + len > contentLength) {
            len = (int) (contentLength - pos);
        }
        final int count = wrappedStream.read(b, off, len);
        pos += count;
        return count;
    }

    /**
     * Read more bytes from the stream.
     *
     * @param b
     *        The byte array to put the new data in.
     * @return The number of bytes read into the buffer.
     * @throws IOException
     *         If an IO problem occurs
     * @see java.io.InputStream#read(byte[])
     */
    @Override
    public int read(final byte[] b) throws IOException {
        return read(b, 0, b.length);
    }

    /**
     * Skips and discards a number of bytes from the input stream.
     *
     * @param n
     *        The number of bytes to skip.
     * @return The actual number of bytes skipped. <= 0 if no bytes are skipped.
     * @throws IOException
     *         If an error occurs while skipping bytes.
     * @see InputStream#skip(long)
     */
    @Override
    public long skip(final long n) throws IOException {
        // make sure we don't skip more bytes than are
        // still available
        long length = Math.min(n, contentLength - pos);
        // skip and keep track of the bytes actually skipped
        length = wrappedStream.skip(length);
        // only add the skipped bytes to the current position
        // if bytes were actually skipped
        if (length > 0) {
            pos += length;
        }
        return length;
    }

    @Override
    public int available() throws IOException {
        if (closed) {
            return 0;
        }
        int avail = wrappedStream.available();
        if (pos + avail > contentLength) {
            avail = (int) (contentLength - pos);
        }
        return avail;
    }

}
